1. Field of the Invention
The present invention relates to a display device provided with a spatial modulator such as a liquid crystal panel.
2. Description of the Related Art
A display device is known which uses a liquid crystal panel having a liquid crystal layer sandwiched between a pair of substrates. The liquid crystal panel includes a color filter whereby it is possible to represent a colored display. Each of the pixels in the liquid crystal panel includes a plurality of color dots (openings), and the color filter has color portions of red, green and blue arranged in these color dots. If a color filter is used, part of light from a light source is absorbed by the color filter to result in a problem of lowering the light utilization efficiency.
For example, Japanese Unexamined Patent publication Nos. 6-317794 and 6-308332 disclose color display devices using a diffraction grating. The diffraction grating separates white light into color rays of red, green and blue oriented at predetermined angles, respectively. For guiding the separated color rays of red, green and blue to the color dots of the respective pixel, a micro lens array is provided. The micro lens array includes condenser elements disposed in correspondence to the pixels of the liquid crystal panel. Alternatively, instead of using the micro lens array, the diffraction grating itself may have a color-separation function and a condenser function (the function of a condenser element).
Since there is no absorption of light when the diffraction grating is used, unlike the color filter, the light-utilization efficiency is higher. Typically the pixel of the conventional liquid crystal panel is of a square shape wherein three color dots are arranged in series, whereby one color dot is of a rectangular shape having a ratio of the horizontal length to the vertical length of 1:3. If a circular spot of color rays condensed by the condenser element and output from the diffraction grating is incident upon the rectangular color dot, the rays are partially cut off on the shorter side of the rectangle although the rays are sufficiently incident on the longer side thereof. Accordingly, the light-utilization efficiency becomes insufficient.
It is necessary for the liquid crystal panel to include as many pixels as possible at a small pitch. The pixels are preferably arranged in various desirable patterns. For example, the three color dots of the pixel may be arranged in a row along a horizontal line, or the three color dots of the pixel may be arranged in a row along a line oblique to the horizontal line.
Generally, the arrangement of the condenser elements should be the same (congruent to) as the arrangement of the pixels. However, there are cases where the arrangement of the condenser elements cannot be the same as that of the pixels since one condenser element must cover three color dots. In the prior art, preferable arrangements of the condenser elements relative to those of the pixels have not been apparent.
If a polarizer is used in the liquid crystal panel, the light utilization efficiency is lowered. Therefore, also in this case, a display device having high light utilization efficiency is desired.
Accordingly, the object of the present invention is to provide a display device having an improved light utilization efficiency.
Another object of the present invention is to provide a display device wherein condenser elements are properly arranged in correspondence to various arrangement of pixels.
A further object of the present invention is to provide a display device having an improved light utilization efficiency while using a polarizing device.
A still further object of the present invention is to provide a display device having a reduced color irregularity while using a filter.
According to the first embodiment of the present invention, a display device comprises a spatial modulator having a plurality of pixels and a periodical structural body having condenser elements corresponding to the pixels of the spatial modulator, and wherein each of the pixels of the spatial modulator comprises a plurality of color dots arranged in a first direction, and a length of a pixel area including a peripheral region encircling the plurality of color dots, measured in the first direction is longer than a length of the condenser element of the periodical structural body measured in the first direction.
By this constitution, when a light is separated into a plurality of color rays in one plane, which are then guided to the color dots of the pixels via the condenser elements, a degree of opening of the color dots becomes greater, resulting in a display device having a higher brightness.
Preferably, a length of the color dots area of the pixel of the spatial modulator measured in the first direction is longer than a length of the color dot area measured in a direction transverse to the first direction.
Preferably, the pixels of the spatial modulator are in a delta arrangement. In this case, the condenser elements of the periodical structural body are in a delta arrangement. Two condenser elements of the periodical structural body arranged in the first direction are grouped with two pixels arranged in the direction perpendicular to the first direction. Or, the condenser elements of the periodical structural body are in a square arrangement. In this case, two condenser elements of the periodical structural body arranged in the first direction are grouped with two pixels arranged in the direction perpendicular to the first direction. The condenser elements of the periodical structural body are substantially of a square shape.
Preferably, the spatial modulator is a liquid crystal panel and the periodical structural body is a diffraction grating. Or, the spatial modulator is a liquid crystal panel and the periodical structural body is a micro lens array.
According to another aspect, the present invention provides a display device comprising a spatial modulator having a plurality of pixels and means for forming an image relating to the pixels of the spatial modulator on a plane spaced from the spatial modulator at a distance, wherein a spatial frequency of the image on the plane is smaller than a spatial frequency of the pixel of the spatial modulator. By disposing a screen on this plane, it is possible to more clearly observe an image formed thereon by the spatial modulator. This feature may be used together with the above-mentioned feature.
According to a further aspect, the present invention provides a display device comprising a spatial modulator having a plurality of pixels and a periodical structural body having condenser elements corresponding to the pixels of the spatial modulator, wherein each of the pixels of the spatial modulator comprises a plurality of color dots; the number of the condenser elements per unit volume being equal to the number of the pixels per unit volume or integer times thereof.
When the display device is structured, the pixels are arranged at a pitch in a two-dimensional manner without any gaps. If the condenser element is of the same shape (congruence) as that of the pixel, the two-dimensional arrangement is possible with no gap. Also, the condenser element may be of a similar figure to the pixel. For example, the shape of the pixel may be minimized or the shape of the condenser element may be enlarged.
An area of the pixel, however, is preferably the same as that of the condenser element. Then, there is naturally a restriction in the combination of the condenser elements with the pixels. A shape of the condenser element is preferably different from that of the pixel, because various combinations of the pixels and the condenser elements are achievable. For example, there may be a combination of pixels in a square arrangement and condenser elements in a delta arrangement; a combination of pixels in a delta arrangement and a condenser elements in a square arrangement; a combination of pixels in a delta arrangement and condenser elements in a delta arrangement; a combination of pixels in a mosaic arrangement and condenser elements in a delta arrangement; or a combination of pixels in a mosaic arrangement and a condenser elements in a square arrangement.
Similar to the pixels, it is necessary to arrange the condenser elements in one plane with no gap. To satisfy this demand and achieve the above-mentioned various combinations, the condenser elements may be of a polygonal shape such as square, rectangle or hexagon. The rectangle has a ratio of a shorter length to a longer length of 1:2, and is oriented at 45 degrees relative to a vertical line. All of interior angles of the polygon are obtuse. The polygon may be a hexagon having pairs or parallel opposite sides and oriented so that a symmetrical axis thereof is oriented at 45 degrees relative to a vertical line. The symmetrical axis may extend in the vertical or horizontal direction. According to a still further aspect, the present invention provides a display device comprising a polarizing device for separating light from a light source into first and second polarized rays having mutually perpendicular oscillating planes and merging the light so that the oscillation plane of one of the first and second polarized rays becomes the same as that of the other while making a predetermined angle between each other, a spatial modulator having a plurality of pixels, a periodical structural body having condenser elements corresponding to the pixels of the spatial modulator, and wherein regarding the first and second polarized rays emerging from the polarizing device and passing through a first condenser element, the first polarized ray is made incident to a first pixel and the second polarized ray is made incident to a second pixel, and regarding the first and second polarized rays emerging from the polarizing device and passing through a second condenser element, the first polarized ray is made incident to the second pixel and the second polarized ray is made incident to a third pixel.
According to this structure, a light is not reduced to one half of a source light by a polarizer in a display device using polarized rays, unlike the prior art device. That is, a light from the light source is separated into first and second polarized rays and output so that the oscillation planes of the first and second polarized rays become the same while making a predetermined angle between each other, whereby both of the first and second polarized rays are usable (i.e., almost all the light from the light source is used). The first and second polarized rays are made incident to all the pixels, whereby even if an expected difference exists in characteristic between both the polarized rays, there is no influence on the displayed image.
According to a yet further aspect, the present invention provides a display device comprising a light source, a spatial modulator having a plurality of pixels, a periodical structural body having condenser elements corresponding to the pixels of the spatial modulator, and a filter having a red-cut function adapted for a spectrum band on longer wavelength side of a red spectrum band and a blue-cut function adapted for a spectrum band on the longer wavelength side of a blue spectrum band.
Preferably, the device further comprises a filter having a wavelength cutting function adapted for an approximately medium wavelength between the red and blue spectrum bands. Also, it further comprises a filter having a wavelength cutting function adapted for an approximately medium wavelength between the green and blue spectrum bands.
Also, a display device according to the present invention comprises a light source, a spatial modulator having a plurality of pixels and a periodical structure body having condenser elements corresponding to the pixels of the spatial modulator, each of the spatial modulator having a plurality color dots arranged in the color-separation direction, and the number of the condenser elements is more than the number of the pixels.
Preferably, the number of cells of the condenser elements (NX, NY) satisfies the following equation:
NXxc3x97NYxe2x89xa7(MX+2)xc3x97(MY+2) 
wherein MX and MY represent the numbers of pixels, each formed by a group of color dots.